MXPA98008249A - Arresting material test apparatus and methods - Google Patents

Abstract

Arresting material test apparatus, test probes and methods enable testing of compressive gradient strength of cellular concrete, and materials having similar characteristics, on a continuous basis from the surface of a section to a typical internal penetration depth of at least 60 percent of thickness. Previous testing of cellular concrete typically focused on determining a minimum structural strength prior to structural failure or shattering of a test sample. For an aircraft arresting bed, for example, cellular concrete must exhibit a compressive gradient strength in a relatively narrow precalculated range continuously from the surface to penetration depth equal to 60 or 80 percent. Precalculated and controlled compressive gradient strength is critical to enabling an aircraft to be safely stopped within a set distance, without giving rise to drag forces exceeding main landing gear structural limits. Test apparatus, test probes with post-compression build-up relief and test methods are described.

Description

APPARATUS AND METHODS OF PROOF OF DETENTION MATERIAL FIELD OF THE INVENTION This invention relates to systems for delaying the movement of vehicles, and more particularly, to apparatus and test methods for testing cellular concrete intended for use in detention bed systems to safely decelerate an airplane that deviates from the end of a runway. .

BACKGROUND OF THE INVENTION An airplane can, and indeed does, invade the ends of the runways increasing the possibility of damage to passengers and destruction or severe damage to the airplane. These invasions have occurred during aborted takeoffs or during landing, with the airplane traveling at speeds of 80 knots. To minimize the dangers of invasions, the Federal Aviation Administration (FAA) of the United States generally requires a safety area of 305 m in length beyond the end of the runway. Although this security area is currently an FFA standard, many tracks in the United States were built before their adoption and are located in such a way that water, roads and other obstacles prevent them from fulfilling the economic requirement of invasion of 305 m.

Several materials, including existing land surfaces beyond the track, have been analyzed to determine their ability to decelerate the airplane. The surfaces of earth are very predictable in their capacity of detention, since their properties are unpredictable. For example, a very dry clay can be hard and almost impenetrable, but wet clay can cause the airplane to get stuck quickly, causing the landing gear to collapse and causing potential damage to the passenger and crew, as well as greater damage to the airplane. A 1988 report handles an investigation by the port authority of New York and New Jersey, E.U. on the feasibility of developing a plastic stop foam for a runway at JFK International Airport in the United States. In the report, it is stated that the analyzes indicated that such a stopping design is feasible and can safely stop a 45 tonne airplane that invades the runway at an exit speed of up to 80 knots and a 369 tonne airplane invading at a speed of exit of up to 60 knots. The report states that the performance of an appropriate plastic detention foam configuration is potentially "superior to a paved invasion area of 305 m, particularly when the arrest is not effective and reverse thrust is not available." As is known, the effectiveness of detention may be limited under wet or icy surface conditions (University of Dayton report UDR-TR-88-07, January 1988). More recently, an airplane stopping system has been described in U.S. Patent No. 5,193,764 to Larrett et al. In accordance with the description of that patent, an airplane stopping area is formed by adhering a plurality of thin layers of rigid, fragile fire-resistant phenolic foam, stacked with each other, with the lowermost layer of foam adhering to a surface support. The stacked layers are designed in such a way that the compressive strength of the combined layers of rigid plastic foam is less than the force exerted by the landing gear of any airplane of the type intended to be stopped when moving in the stopping area of the aircraft. a track, in such a way that the foam is crushed when it makes contact with the airplane. The preferred material is phenolic foam used with a compatible adhesive such as a latex adhesive. Tests of phenolic foam-based detention systems indicate that, although these systems can function to stop an airplane, the use of foam material has disadvantages. The main one among the disadvantages is the fact that the foam, depending on its properties, it can typically exhibit a bounce property. Thus, it was observed that in stopping bed tests with phenolic foam some forward thrust occurs to the wheels of the airplane as it moves through the foam material, as a result of bouncing of the foam material on its own. Foam or cellular concrete has been suggested as a material for use in detention bed systems, and has undergone a limited field analysis in the prior art. These tests have indicated that cellular concrete has good potential for use in detention bed systems, based on the provision of many of the advantages of phenolic foam, while avoiding some of the disadvantages of phenolic foams. However, the requirements of a crush resistance and uniformity of material controlled exactly throughout the detention bed are critical and as far as is known, the production of cellular concrete of appropriate characteristics and uniformity has not been achieved or described above. The production of structural concrete for building purposes is an old technique that includes relatively simple treatment steps. The production of cellular concrete, although it usually includes simple ingredients, is complicated by the nature and effect of the aeration, mixing and hydration aspects, which must be closely specified, and accurately controlled if a uniform final product is to be produced. it is neither too weak nor too strong for present purposes. Discontinuities, including areas of weaker and stronger cellular concrete, can actually cause damage to the vehicle that decelerates if, for example, deceleration forces exceed the strength of the wheel support structure. This lack of uniformity also results in an inability to accurately predict the deceleration performance and the total stopping distance. In a recent feasibility test using commercial grade cellular concrete, an airplane equipped to record run test data overland was acquired through a bed section and load data. Although actions have been taken to try to provide uniformity of production, the samples taken and the airplane load data from the test detention bed showed significant variations between the areas where the resistance to crushing was excessively high and areas in which it was excessively low. Obviously, the potential benefit of a detention system is compromised if the airplane is exposed to forces that could damage or crush the main landing gear. In this way, although the detention bed systems have been considered, and some real tests of several materials have been explored for the same, the production and practical implementation of a detention bed system has not been achieved. the distances specified, safely detain the airplane of known size and weight that moves at a speed regime projected outside a runway, nor suitable materials to be used in the same. The amount of material and the geometry in which it is formed to provide an effective stopping bed for vehicles of predetermined size, weight and speed depends directly on the physical properties of the material and in particular on the amount of drag that will be applied. the vehicle as it moves through the bed crushing or otherwise deforming the material. Computer programming models or other techniques can be used to develop entrainment or deceleration objectives for detention beds, based on the calculated forces and absorption energy for an airplane of particular size and weight, in view of the corresponding resistance specifications of the aircraft. Landing gear for said airplane. Nevertheless, the models must assume that the detention bed is constructed of a material that has a uniformity from section to section and from batch to batch of characteristics, such as strength, durability, etc. to produce uniform results with a predictable amount of energy absorption (entrainment) when it makes contact with the portions of the airplane (or other vehicle) that carry the vehicle's load through the bed (for example the wheels of an airplane as it moves to through the bed after having invaded the track). One of the potential benefits of the use of cellular concrete or foam in detention bed systems, is that the same material is capable of being produced in a variety of different ways using numerous different starting materials. For previous types of applications unrelated to vehicle deceleration, concrete has been produced using a particular type of cement (usually Portland) that is combined with water, a foaming agent, and air to produce a cellular concrete. However, a significant distinctive requirement separates these prior applications for cellular concrete from the production of a product suitable for use in a detention bed. In prior applications, the targets are typically reduced weight or cost, or both, while providing a predetermined minimum strength, with better resistance being better. Previous applications typically have not required the production of cellular concrete at strict standards of both maximum strength and minimum strength. Also, previous applications have not required a high degree of uniformity of the material, as long as the basic resistance objectives are met. Even for previous applications of cellular concrete, it is known that the quantity and type of cement, the water-cement ratio, the amount and type of foaming agent, the manner in which the materials are combined, the treatment conditions and the conditions of healing, have all critical effects on the resulting properties of cellular concrete. The need to refine production to the levels required to produce adequate cellular concrete for vehicle stowage beds has not been presented in the above applications.

Thus, an object is to specify the objectives as regards the mechanical properties of the appropriate materials in order to obtain the desired deceleration when an airplane or other vehicle enters the detention bed. However, it is not known that the ability to consistently produce a cellular concrete material having actually the required properties of predetermined strength and uniformity has been previously achieved. A substantial problem in the technique is the lack of established techniques for the production of cellular concrete in the low resistance scale, in a uniform manner, to very narrow tolerances, to allow the construction of a whole detention bed that has consistently the mechanical properties desired in all its geometry. Although the pouring of cellular concrete into the site has been suggested, a practical design for the successful realization of a cellular concrete stopping bed has not previously been provided. Another problem is to determine in advance what mechanical forces the vehicle actually experiences as it moves through foam concrete of a particular degree of manufacture. The mechanical properties of interest are not the strength of the material, per se, but rather the deceleration force experienced by an object moving through the material as the material deforms. More conventional tests of concrete samples measure the fracture resistance of the material, to establish at least a specified load to be supported. In contrast, in stopping bed technology, the important feature is the energy absorbed on a continuous basis during the compressive failure of the material (ie, the actual resistance during continuous compressive failure). Without an appropriate testing methodology that can be used to determine on a continuous basis the compressive strength that will be provided by a particular formula, production technique, cure and design, the technique would be left with the need to build very tight detention bed structures. costly with a variety of different samples of cellular concrete, in an effort to determine which of these, when used as a real detention bed, works in a way that could be predicted. More particularly, since in the past structural cellular concrete applications could be supported by minimum strength tests, neither adequate test methods nor apparatus have been provided to allow reliable and continuous testing of compressive strength by a depth of penetration from the surface of a section of cellular concrete and continuing to an internal depth of penetration up to 80% of section thickness. The objects of the invention are to provide new and improved apparatus and test methods for testing cellular concrete stopping material, and such apparatus and test methods that provide one or more of the following advantages and capabilities: -dependent determination of the gradient of resistance to compression that will be experienced when a moving object slows down; -test the compression strength without structural collapse of a test sample; -Continuous determination of the gradient of compressive strength of the surface of a sample up to an internal penetration thickness of the order of 70% of the thickness of the sample. -register the test pressure to the compressive failure and the depth of penetration in a continuous base. -using an improved test probe head, driven by a penetration arrow; and - using a penetration arrow having an arrow portion of restricted cross section to reduce the effects of accumulation of material after compression that can distort the accuracy of the data obtained.

BRIEF DESCRIPTION OF THE INVENTION In accordance with the invention, an apparatus for testing detention material, to test the compression strength gradient continuously from the surface to an internal depth of penetration within the compressible stop material, includes a penetration arrow having a length no less than the internal depth of penetration and a cross-sectional size . A test probe head is connected to the penetration arrow and has a compressive contact surface. The penetration arrow includes a restricted portion of the arrow, starting behind the test probe head and continuing at least part of the length of the penetration arrow. This restricted arrow portion typically has a cross-sectional area at least 10% smaller than the area of the contact surface of the test probe, to reduce the accumulation of material after compression behind the probe probe head and the distortion of data that originate from such accumulation. A pulse mechanism is coupled to the penetration arrow to move the arrow and propel the test probe head to the internal depth of penetration into the stop material. A displacement sensing device coupled with the penetration arrow is provided to detect displacement thereof. A load sensing device, coupled with the penetration arrow, detects the pressure exerted against the contact surface of the test probe as it compresses the stop material towards the internal depth of penetration. The apparatus also includes a pressure sensitive data acquisition device detected by the charge detecting device, and sensitive to the depth of penetration of the contact surface of the test probe, to provide representative data of continuous measurement of the gradient of the test probe. Compressive strength of the compressible stop material subjected to the test. Also in accordance with the invention, a stop material test probe, suitable for testing the gradient of compressive strength continuously from the surface to an internal depth of penetration within the compressible stop material, includes a penetration arrow, head of test probe and restricted arrow portion as described above. The cross-sectional area and the length of the restricted portion of the arrow are selected as appropriate to reduce the accumulation effects after compression behind the contact surface, as it travels from the surface to an internal depth of penetration into the material of detention under test. This depth of penetration can typically be at least 60% the thickness of a section of the stopping material to be tested. Also in accordance with the invention, a method for testing the continuous compressive failure of a section of cellular concrete suitable for use in stopping vehicles, includes the steps of: (a) providing a penetration arrow carrying a test probe head with a contact surface that has a contact surface area; (b) provide a test section of cellular concrete that has a thickness and has a cross-sectional area at least times larger than the contact surface area; (c) holding the test section longitudinally; (d) propelling the contact surface of the test probe head longitudinally into the test section from a surface to an internal depth of penetration into the test section; (e) monitoring on a continuous basis the displacement of the probe probe head; and (f) monitoring the compressive force on said contact surface in a plurality of intermediate penetration depths within the test section. For a better understanding of the invention, together with other additional objects, reference is made to the appended drawings, and the scope of the invention will be pointed out in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 illustrates one embodiment of the detention material testing apparatus according to the invention.

Figures 2 and 4 are respectively side and bottom views of a test probe head and a portion of an associated penetration arrow using the invention. Figure 3 is a side view showing a test probe head mounted to a penetration arrow of an alternative construction according to the invention. Figure 5 is a flowchart useful in describing a test method in accordance with the invention. Figures 6 and 7 show the data obtained using the apparatus of Figure 1 and the method of Figure 5, in terms of the compressive force indicated along the ordinate against the percentage of penetration indicated along the abscissa , for samples of cellular concrete of two different resistances.

DETAILED DESCRIPTION OF THE INVENTION The use of cellular concrete in detention bed applications requires that the material is generally uniform in its resistance to deformation, since it is the prediction of the resistance forces acting on the surface of the contact members of the vehicle that is being used. decelerated, which allows the bed to be designed, sized and constructed in a way that will guarantee acceptable performance. To obtain such uniformity, there must be a careful selection and control of the ingredients used to prepare the cellular concrete, the conditions under which they are processed, and their curing regime. The cellular concrete ingredients are generally a cement, preferably Portland cement, a foaming agent, and water. In some circumstances, relatively fine sand or other materials may also be used, but these are not used in the currently preferred embodiments. For the present purposes, the term "cellular concrete" is used as a generic term that encompasses concrete with cells or relatively small internal bubbles of a fluid, such as air, and which may include sand or other material, as well as formulations that do not include said sand or other material. There are many known methods for producing cellular concrete. In general, the process includes the steps of mixing the foam concentrate with water, generating foam by means of inductive air, adding the resulting foam to the cement paste or slurry of cement / aggregate, and uniformly mixing the foam paste and cement in a controlled manner, which results in a homogeneous mixture with a significant number of voids or "cells" that keep the density of the material relatively low compared to other types of concrete. The uniform foaming, mixing and setting of the materials is of extreme importance because the application of cellular concrete for detention bed applications requires a general uniformity of the properties of the material. The construction of the detention bed system can be done by producing the cellular concrete in a production facility or in the bed site, and pouring the concrete into shapes with appropriate dimensions to achieve the desired geometry for the system. Nevertheless, for the purpose of uniformity of material characteristics and total quality control, it has been found preferable to cast sections of the total bed using shapes of appropriate size and then transport the sections to the site and install them to form the total configuration of the bed. In the latter case, these units or sections in the form of blocks of predetermined sizes can be produced and maintained until the completion of the quality control test. The blocks can then be transported to the site, placed in their position and adhered to the runway safety area using asphalt, cement slurry or other suitable adhesive material, depending on the construction materials of the same safety area.

Definition of "Compression Resistance Gradient", or "CGS" It is commonly understood that the term "compressive strength" (not CGS) means the amount of force (conventionally measured in kilograms per square meter) which, when applied to a normal vector to the surface of a standardized sample, will cause the sample to fail. Most conventional test methods specify test apparatus, sampling procedures, test specimen requirements (including size, molding, and cure requirements), load rates, and record keeping requirements. An example is ASTM C 495-86"Standard Method for Compressive Strength of Lightweight Insulating Concrete". While such conventional test methods are useful when designing structures that are required to maintain structural integrity under predicted loading conditions (i.e., having at least a minimum resistance), the purpose of the detention bed systems is its failure in a predictable specified way, thus providing predictable controlled strength of resistance as the vehicle deforms the cellular concrete (ie, a specific gradient of compressive strength). Thus, said conventional test focuses on determining the resistance to a point of failure, not the resistance during compression failure. Put more simply, knowing how much force will fragment a specimen of cellular concrete material does not answer the critical question of how much entrainment or deceleration will be experienced by a vehicle moving through a detention bed system . In contrast to a "punctual" fracture resistance as in the prior art, for the present purposes, the test should evaluate a continuous mode of compression failure as a portion of a specimen is continuously compressed to approximately 20% of its original thickness . Generally, there have not previously been adequate equipment or methods for such continuous testing appropriate for the present purposes. Due to the wide range of available materials and cellular concrete processing variables, and the magnitude and cost to build stopping beds for testing, it is imperative that there is accurate test information to predict the amount of strength of resistance that a particular variety of cellular concrete, processed and cured in a certain way, will provide when used in a detention bed system. Through the development of new test methodology to focus the resulting data on the measurement of the strength of resistance that occurs during failure to the continuous compression of a sample, instead of the simple "compressive resistance", have been developed new test methods and apparatus to allow reliable testing and confirmation of cellular concrete materials and appropriate process variables. As a result, it has been determined that the compression force needed to crush cellular concrete up to 20% of its original thickness varies with the depth of penetration. This feature, which the present inventors termed "compression strength gradient" or "CGS", must be precisely specified to construct a vehicle stopping bed made of cellular concrete having known deceleration characteristics to retard with security an airplane. The method and test equipment of the present invention provide load and strain data for cell concrete test samples, or materials with similar characteristics, which can be used to predict exactly how the performance of a dwell bed constructed of the same material will be. Thus, a penetration type test method, where the compressive strength of a sample of cellular concrete is measured, not applying a force that will fracture a sample, but rather will continuously report information about the resistance forces generated as a test probe head, which has a specified compressive contact surface, moves through a volume of cellular concrete, is key to obtaining the data needed to formulate and use cellular concrete in detention bed applications. As measured thus, the CGS will fluctuate on a scale with penetration depth, resulting in a gradient value (such as CGS of 60/80), rather than a single singular fracture value as in the previous tests. For the present purposes, the term "compression strength gradient" (or "CGS") is used to refer to the compressive strength of a section of cellular concrete from a surface and continuing to an internal depth of penetration that typically It can be 66 percent of the thickness of the section. As defined, the CGS does not correspond to the compressive strength determined by standard ASTM test methods.

Test Apparatus of Figure 1 Referring now to Figure 1, one embodiment of the stopping material testing apparatus according to the invention is illustrated. As will be described later, the apparatus of Figure 1 is arranged to continuously test the compressive strength gradient of the surface at an internal depth of penetration into a sample section of the compressible stop material. As shown, a structural platform base 2 is included, suitable for supporting the lower part of a test section and forming a test support structure in combination with frame side members 4. A piston, in the form of a penetration arrow 6, is slidably coupled in the cylinder 8 and arranged for activation by the fluid coupled through hydraulic lines 10. The configuration is such that an arrow 6 can be driven downwardly towards a test section 12 of cellular concrete or other suitable material in reaction for the activation of the hydraulic pressure source 14. The test section 12 is held during the test by means of a lower support block 16 resting on the base 2. A head of Test probe mounted on the bottom of the penetration arrow 6 will be described with reference to Figures 2-4. It will be appreciated that the hydraulic cylinder 8, fed by the lines 10 of the hydraulic pressure source 14, comprises a form of drive mechanism coupled to the penetration arrow 6, and provides the ability to continuously move the arrow 6 to drive a test probe head at an internal depth of penetration into a test section of the stopping material 12. As illustrated, the test apparatus further includes a load sensing device shown as the load cell 18. The load cell 18 is arranged in a known manner to measure the force exerted on the penetration arrow 6 and the contact surface of the test probe head, as it moves towards the cellular concrete of the test section 12 and causes its compressive failure. Alternatively, the measured force can be considered as a measure of the resistance provided by the cellular concrete against the contact surface of the test probe head during the compressive failure of the test section 12. The forces measured by the load cell which comprises the charge detecting device 18, are continuously monitored and can be recorded in terms of force or pressure during the test by the data line 20 coupled to a data acquisition device 22. In Figure 1, the test apparatus it also includes a displacement sensing device, shown as a linear potentiometer 24, arranged in such a way that its impedance varies with changes in the position of the penetration arrow 6. The displacement sensing device 24 is coupled to the acquisition device of data 22 through data line 26 to allow the displacement of arrow 6 to be monitored and recorded continuously during the test. In the illustrated test apparatus, the hydraulic pressure detected by a pressure sensing device, shown as pressure transducer 28, is also monitored and recorded by the data line 30. Referring now to FIGS. 2-4, it is shown in FIG. more detail two exemplary configurations of a detention material test probe according to the invention, which are suitable for continuously testing the compression resistance gradient from the surface to an internal depth of penetration into the arresting material. The test probe comprises a penetration arrow and a test probe head mounted at the lower end thereof. Figure 2 shows the lower portion of a penetration arrow 6 having a total length no greater than the internal penetration depth during the test, and a cross-sectional size represented by the diameter 7. The penetration arrow 6 may typically be formed of steel and have a circular cylindrical shape. The test probe head 34 is suitably connected to the lower end of the arrow 6 (for example, fixed thereto by means of welding, screwed on the end, etc.), so as to remain in position when exposed to longitudinal pressure. The test probe head 34 has a compressive contact surface 36, which can be hardened or otherwise adapted to compress cellular concrete or other material, without excessive deformation of the surface 36. The size of the contact surface 36, shown by the diameter 35 indicated in the bottom view of Figure 4, it is larger than the cross-sectional size of a restricted portion of the penetration arrow '6. In Figure 2, it will be seen that the diameter of the contact surface 35 is larger than the diameter 7 of the arrow 6, which in this example is of uniform diameter over its length. Figure 3 shows an alternative configuration. In Figure 3, the penetration arrow 6A has a basic diameter 7A which coincides with the hydraulic cylinder 8 of Figure 1. The penetration arrow 6A includes a restricted portion 6B of arrow of smaller cross-sectional area, starting behind the test probe head 34 and continues for at least a part of the length of the penetration arrow. Thus, with reference to Figure 2, it will be noted that in the first configuration, the restricted portion of the arrow having a reduced cross-sectional area relative to the contact surface 36, effectively extends over the entire length of the penetration arrow, as also illustrated in Figure 1. In Figure 3, the restricted portion of the arrow represents only part of the length of the arrow 6A. According to the invention, it has been found that the provision of a restricted portion of the arrow extending behind the probe probe head is effective in reducing the potential effects of error-producing, post-compression accumulation of particles. of cellular concrete behind the contact surface as it moves towards the detention material under test. Preferably, the restricted portion of the arrow will have a length at least equal to the intended penetration depth. It has been found that this feature increases the accuracy and reliability of the test results as an indication of the actual compression resistance gradient experienced in the use of the detention material. A presently preferred configuration of the test probe head 34 includes a flat circular contact surface 36 of approximately 5 cm in diameter with the restricted arrow portion (6 or 6b) behind the head 34 with a cross sectional area 10 to 50 one hundred times smaller than the contact surface, and continuing behind the test probe head 34 at a distance at least equal to the depth of penetration. The construction must have a basic structural integrity and adequate contact surface hardness to withstand compression pressures of at least 7 and preferably 35 kg / cm2, without failure or significant surface distortion. In other embodiments, the contact surface 36 may have a hexagonal or other suitable shape and be of any appropriate size. In this regard, however, it is currently considered preferable that the size of the contact surface 36, relative to the cross-sectional size of the test portion 12, be such that the test can be completed without general structural failure or fracture of the test portion. the test sample, such as thinning of the side portions of the test portion 12, before approximately 70% penetration. According to the invention, in order to obtain exact results indicative of the compression resistance gradient in use of the detention bed, it is currently preferred that the test portion 12 be held only from the bottom without lateral support, enclosure or enclosure, and remain intact during the test except for internal compressive failure along the path of the test probe head 34. General structural failure or fragmentation of the test sample after 70 or 80% penetration is typically not interest to validate the test results. Using a test method in which the sample is not restricted as the piston penetrates and exerts the resulting stresses, a closer approximation to the performance of the stopping test bed is achieved, since there will be no restriction or reflection of tension force caused by cellular concrete or other material under the test being forced up against an artificially resistant container wall.

Test method of Figure 5 The test methodology includes the ability to measure the load dynamically as the test probe head moves through the sample. In a preferred method, the load is applied at a relatively high constant velocity with force measurements occurring continuously or at small increments of displacement as the probe probe head moves through the sample. A currently preferred test probe head travel speed is approximately 150 cm per minute, which is relatively fast compared to the specified 0.105 cm per minute for the different test form specified in the standard test procedure C39-86. . The samples of cellular concrete that are deformed in this way will reach a point of deformation in which essentially all the hollow spaces or cells have been crushed and the amount of compressive force necessary for additional deformation will rapidly increase, or the test sample will experience general structural failure. That point typically occurs at a penetration depth of order of 80% of the sample thickness. The forces that are necessary to deform the sample from an initial point to the point at which this rapid increase in compression force occurs (for example to at least 60% of the thickness of the sample), are the forces of interest and that the methodology and the test apparatus must look for their catch. Thus, it will be appreciated that an object of the present invention is to provide test results indicative of deceleration that will be experienced by a vehicle or other object moving through a volume of compressible stopping material. This objective differs from the objective of prior art test approaches that are inadequate for present purposes. According to the invention and with reference to Figure 5, a method for testing the gradient to continuous compression of a section of cellular concrete suitable for use in vehicle detention, comprises the following steps: a) provide, step 40 in the Figure 5, a penetration arrow carrying a test probe head with a compressive contact surface having a contact surface area; b) providing, step 42, a test section of cellular concrete having a cross-sectional area at least 20 times larger than the contact surface area and having a thickness; c) supporting the test section longitudinally, step 44; d) driving the contact surface of the test probe head, step 46, longitudinally towards the test section from the upper surface to an internal depth of penetration within the test section; e) monitor, step 48, the displacement of the probe probe head; and f) monitoring, step 48, the compressive force on said contact surface at a plurality of intermediate penetration depths within said test section. The method may additionally include the step of making available a presentation of a gradient representing compression force values at a plurality of intermediate depths, as will be described with reference to figures 6 and 7. The presentation may take the form of a graph of computer as in figures 6 and 7, a comparable display on a computer monitor or other suitable form. In the application of this test method, step (c) preferably comprises holding the lower part of the test section, in the absence of lateral restriction of the sides of the test section. Also, step (d) preferably comprises driving the contact surface continuously to an internal penetration depth equal to at least 60% (and typically up to about 70%) of the thickness of the test section, and in step (e) ) the force on the contact surface of the test probe head is preferably recorded at short intervals (for example 10 to 30 times per second) until the contact surface reaches said internal depth of penetration. The apparatus is arranged to apply the load to the sample continuously rather than intermittently, and without shock. The loading speed must be adjustable, preferably controllable through software operation by means of data acquisition which may for example be a general-purpose personal computer with appropriate data acquisition software. Preferably, the apparatus provides a prescribed load speed for the entire travel during the penetration of the test section. The length of travel varies depending on the thickness of the section, with a longer load path length for a greater penetration depth as appropriate for thicker test sections. Load information, distance information and pressure information are acquired by the data acquisition means during penetration and can be sampled and recorded at a rate of 30 times per second for each individual test. In other applications, the sampling rate may be different. Although tolerances must be specified as appropriate in particular embodiments, a test specification can provide a maximum allowable error at any point for the load of 1.35 in 450 kg, for distance 0.16 cm in 60.96 cm, and for pressure 0.07 to 70 kg / cm2. The verification of the accuracy of the operation and the acquisition of data must include proof across the entire loading scale. The data acquisition software used in the data acquisition computer can be arranged and configured by the experts, in such a way that it is effective to monitor all the information received from each device detecting the device. Preferably, the software should allow the use of a deployment to allow the operator to display and continuously observe the data as the test proceeds. The data to be recorded includes representative readings of load (pounds), displacements (inches), time (seconds) and preferably also hydraulic pressure (lb / in2). Data should typically be sampled at short intervals (for example, 30 readings per second). This should occur for the complete travel of the test probe head as the sample penetrates. In certain configurations, the hydraulic pressure can not be monitored, or it can be used as base data or substitutes for load data. To provide maximum accuracy, the zeroing and adjustment of the test apparatus must be monitored and recorded by means of the data acquisition software. It may be convenient to record the new input data directly and also make the data automatically available in converted form. Thus, for example, loading data with respect to the contact surface force can typically be recorded in pounds and converted into pounds per square inch by factoring between the contact surface area. Similarly, a voltage output representative of resistance from the displacement detector 24 can be converted into inches of displacement. The preparation of uniform samples and careful registration regarding their characteristics is an important part of the testing process. Certain specific observations can be made with respect to the testing process. Cellular concrete sampling may, for example, use the appropriate provisions of the ASTM C-172 method with the following exceptions: when sampling from a pump equipment, a bucket of approximately 19 liters capacity must be filled by passing it through the discharge current of the concrete pump hose used to place the concrete at the point of concrete placement. Care should be taken to ensure that the sample is representative of the discharge, avoiding the start or end of the equipment discharge. The test specimens should then be prepared, as described below, by pouring light weight concrete from the cuvette. In addition, remixing of samples in this test procedure should not be allowed. Typically, the test specimens may be 30.48 cm cubes or have other suitable three-dimensional shapes. The specimens are molded by placing the concrete in a continuous and forced pouring manner. The molds should be shaken gently as the material is added. The concrete should not be rocked. The specimens should not be shaved immediately after filling the molds. They should be covered in such a way as to avoid evaporation without damage to the surface. The specimens should not be removed from the mold until they are tested. The curing of the specimens should conveniently occur at approximately the same curing temperature as that used for the section of the detention bed of which the specimens are representative. The specimens should remain covered, to restrict evaporation for at least 21 days or to test their compressive strength, consistent with the healing of the corresponding detention sections. In preparation for the test, the specimen must be removed from the mold and placed under the test probe head. The top surface should have a smooth surface to accommodate the face of the probe head contact surface. The surface of the specimen in contact with the lower support block of the test machine must be sufficiently flat to be stable and prevent skewed movement of the piston during the test. Before the test, the specimen must be weighed and measured along three axes (height, length, width). Then, these dimensions are used to calculate the density with respect to the test time. At the time of testing, the contact surface of the test zone head and the surfaces of the lower support block must be clean, and the sample must be carefully aligned in such a way that the test zone head passes through the Approximate center of the specimen. As the contact surface is initially carried to rest on the specimen, the specimen placement should be adjusted gently by hand. Then continuous charging should be applied without shock at a constant speed, typically 2.5 cm per second. The data points are preferably recorded up to the complete depth of penetration. The type of any failure and the appearance of the concrete is recorded at the end of the test, and are preferably included with the test data. The compression resistance gradient data is calculated by dividing the load at the data point between the surface area of the piston. Typically data points are discarded during the initial displacement to approximately 10% of the thickness of the test section, and the data that is captured after the specimen reaches a fully compressed state, as they are less reliable than the test data remaining. The penetration depth must be calculated by subtracting the piston displacement in initial contact from the last data point of the piston displacement. With reference to figures 6 and 7, examples of test data recorded during the test of cellular concrete samples are shown. In this case, the test samples were of a cube size and shape of approximately 30.48 cm. Test data were derived using a test probe head having a flat circular contact surface, with a load cell used to measure loads through 75% of the total thickness of the sample. Figure 6 illustrates the CGS characteristics of a sample of cellular concrete representative of a stop block, determined by the test. In Figure 6, the lower scale represents percent penetration of test probe expressed in tenths of sample thickness or height. The vertical scale represents the compression force of the test probe expressed in kilograms per square centimeter (kg / cm2). The test data of interest are typically within the penetration range of 10 to 60% of the sample thickness. Data outside this scale may be less reliable, with total compression effects occurring beyond approximately 70% penetration. As illustrated in Figure 6, the resistance to failure of cellular concrete exhibits a gradient with resistance to compression increasing with the depth of penetration. The line through points A and B in Figure 6 represents a 60/80 CGS, that is, a CGS characterized by a compressive strength changing linearly from about 4.20 kg / cm2 to about 5.60 kg / cm2 on a penetration scale from 10 to 66%. The average, on this scale is thus approximately 4.90 kg / cm2 at the midpoint C. The lines of D and E represent quality control limits and the F line represents actual test data recorded for a specific test sample of concrete cell phone. In this example, a test sample for which the test data on a penetration scale of 10 to 66% remains within the quality control limit lines D and E, represents a stop block manufactured within acceptable tolerances. . Figure 7 is a similar illustration of the CGS characteristics of a test sample of a CGS 80/100 stop block. Although the presently preferred embodiments of the invention have been described, those skilled in the art will recognize that further modifications and modifications may be made without departing from the invention, and it is intended to claim all modifications and variations that come within the scope of the invention.

Claims (21)

1. NOVELTY OF THE INVENTION CLAIMS 1. - Stop material test apparatus for providing a gradient of compressive strength on a continuous basis, from the surface to an internal depth of penetration within the compressible stop material, comprising: a penetration arrow having a longer length that said internal depth of penetration and? cross section size; a test probe head connected to said penetration arrow and having a compressive contact surface; said arrow of penetration includes a restricted portion of arrow that begins behind said test probe head and continues up to at least a portion of said length, said restricted portion of arrow having a smaller cross-sectional area than the area of said test surface. contact of said test probe; a pulse mechanism coupled to said penetration arrow to move said arrow to drive said test probe head to said internal penetration depth within the stopping material; a displacement sensing device coupled with said penetrating arrow to detect displacement thereof; and a load detecting device coupled with said penetrating arrow to detect the force exerted against said contact surface of the test probe as it compresses the stop material to said internal penetration depth. 2.- Detention material test apparatus according to claim 1, further characterized in that it comprises: a force-sensitive data acquisition device detected by said load detecting device and the penetration depth of said contact surface the test probe, to provide data representative of the gradient of the compressive strength of said compressible stop material, from the surface to said depth of penetration. 3. Apparatus for testing detention material according to claim 1 or 2, characterized in that said apparatus is arranged to drive said test probe head to an internal depth of penetration of at least 60% of the thickness of the material of detention. 4.- Stop material test apparatus according to any of the preceding claims, characterized in that said test probe head has a flat contact surface and said restricted portion of the arrow has a cross sectional area of at least 10% smaller than the area of said contact surface. 5.- Stop material test apparatus according to any of the preceding claims, characterized in that said test probe head has a flat circular contact surface with an area on a scale of 6.45 to 25.80 cm2. 6.- Detention material testing apparatus according to any of the preceding claims, characterized in that said restricted portion of the penetration arrow continues behind said test probe head until at least the intended depth of penetration and has a cross-sectional area on the scale of 10 to 50% smaller than said contact surface. 7. A stop material test probe, suitable to continuously provide the gradient of compressive strength from the surface to an internal depth of penetration into the compressible stop material, comprising: a penetration arrow having a length not less than said internal depth of penetration and a cross-sectional size; and a test probe head connected to said penetrating arrow and having a compressive contact surface; said arrow of penetration includes a restricted portion of arrow, beginning behind said test probe head and continuing up to at least a portion of said length, said restricted portion of arrow having a cross-sectional area smaller than the area of said contact surface of said test probe; the smaller cross-sectional area of said restricted arrow portion is effective to reduce the effects of distortion by the concentration of material after compression behind said contact surface as it moves from the surface of said internal penetration depth within the Compressible stopping material under test. 8. A stop material test probe according to claim 7, characterized in that said test probe head has a flat circular contact surface. 9. A test probe of detention material according to claim 7 or 8, characterized in that said test probe head has a "flat contact surface with an area on a scale of 6.45 to 25.80 cm2. A detention material test probe according to claim 7, 8 or 9, characterized in that said restricted arrow portion of said penetration arrow continues behind said probe head probes to at least the intended depth of penetration and has a cross-sectional area on a scale of 10 to 50% smaller than said contact surface 11.- A method for continuous compressive testing of a section of cellular concrete suitable for stopping movement of an object, comprising the steps of: a) providing a penetration arrow carrying a test probe head with a compressive contact surface having a contact surface area; a cellular concrete test section having a thickness and having a cross-sectional area larger than said contact surface area; c) holding said test section longitudinally; d) driving said contact surface of said test probe head longitudinally in said test section, from a surface to an internal depth of penetration within said test section; e) monitoring the displacement of said test probe head; f) monitoring the compressive force on said contact surface in a plurality of intermediate penetration depths within said test section. 12. A method according to claim 11, characterized in that step (a) comprises providing said penetrating arrow with a restricted portion of arrow starting behind the probe probe head, said restricted portion of arrow having a transverse area smaller than said contact surface area, said smaller cross-sectional area is effective to reduce the effects of distortion of the concentration subsequent to the compression of material behind said test probe head during the penetration of said section of concrete cell phone. 13. A method according to claim 11 or 12, characterized in that said penetrating arrow is provided with an arrow portion having a cross-sectional area on the scale of 10 to 50% smaller than the contact surface area. 14. - A method according to claim 11, 12 or 13, characterized in that step (a) comprises providing said test probe head with a flat circular contact surface. 15.- A method in accordance with the claim 11, 12, 13 or 14, characterized in that step (a) comprises providing said test probe head with a flat contact surface having a contact surface area on a scale of 6.45 to 25.80 cm2. 16.- A method according to the claim 11, 12, 13, 14 or 15, characterized in that step (d) comprises driving said contact surface continuously to an internal depth of penetration equal to at least 60% of the thickness of said test section. 17.- A method according to the claim 11, 12, 13, 14, 15 or 16, characterized in that step (f) comprises registering the pressure on the contact surface of said test probe head on a continuous basis until said contact surface reaches an internal depth of penetration of at least 60% of the thickness of said test section. 18. A method for determining the gradient of compressive strength over a penetration depth of a test section, comprising the steps of: a) driving a contact surface in said test section to an internal penetration depth of at least 60% of the thickness of said test section; b) during step (a), recording a measure of the compressive force on said contact surface for a plurality of intermediate penetration depths within said test section; and c) making available a presentation of a gradient representing the values of the compression force in said plurality of intermediate depths of penetration. 19. A method according to claim 18, characterized in that step (a) comprises driving a contact surface towards a test section of cellular concrete. 20. A method according to claim 18 or 19, characterized in that the step includes using a contact surface having an area not greater than 5% in cross-sectional area of said test section. 21. A method according to claim 18, 19 or 20, characterized in that step (b) comprises registering the compression force, at least 10 times per second while step (a) is performed.