ICAP 97 78th TRB 99 Session 440 Latest Developments on Tyre Road Surface Interface Stress Measurements Using the 3-D Cell (PP99-3486) Morris De Beer () Louw Kannemeyer (SANRA Ltd)
(1st Reference: 8th ICAP 97- Seattle, USA ICAP 97 Stress - In - Motion (SIM)N, Transportek, South Africa
ICAP 97 RUTTING
ICAP 97 Longitudinal Flow of Asphalt
ICAP 97 Fatigue Cracking and aging
ICAP 97 SURFACE DISINTEGRATION
ICAP 97 TIRES
ICAP 97
ICAP 97
ICAP 97
% OF TYRE PRESSURE 25 ICAP 97 20 Average: 620 kpa (1974) 15 10 Average: 733 kpa (1995) 5 0 200 400 600 800 1000 1200 1400 TYRE INFLATION PRESSURE (kpa) FIGURE 1a Tyre inflation pressure distributions in South Africa (1974-1995)
Heavy vehicles: Axle Loads > 7 000 kg Survey: 1995 ICAP 97 1.2% 9.7% 38.5% 13.8% 3.6% 33.2% 9.00-11.00-20 11.00-R20 11.00-R22.5 12.00-R22.5 275/80-315/80 R22.5 385/80-445/65 R22.5 FIGURE 1b Distribution of heavy truck tyre types in South Africa
VERTICAL CONTACT STRESS (kpa) ICAP 97 Direction of travel TYRE ON HVS (or Vehicle) VRSPTA X Y Pavement Surface 1 2 3 4 5 6 Computer set-up Z 1 2 3 4 5 6 1600 1500 1400 1300 1200 1100 1000 900 800 700 600 500 400 300 200 100 0 SMOOTH TYRE - Z DIRECTION (CREEP SPEED) (JUNE 1994) LOAD 20kN 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 VRSPTA PIN NUMBER FIGURE 2 Schematic layout of VRSPTA system
VEHICLE-ROAD SURFACE PRESSURE TRANSDUCER ARRAY (VRSPTA)
315/80 R22.5 HVS TYRE ON VRSPTA
425 /65 R22.5 HVS TYRE ON VRSPTA
VRSPTA PIN OUTPUT (NEWTON) ICAP 97 600 500 400 300 200 100 Data Regression 0 0 1 1.5 2 2.5 3 3.5 VOLTAGE FIGURE 3 Laboratory calibration data of VRSPTA pins
17 mm 15 mm ICAP 97 Effective Area = 250,28 mm 2 Direction of tyre movement Support pins Instrumented pins FIGURE 4 Effective Diamond Shaped Area used for the contact stress calculation in VRSPTA
VRSPTA MEASURED LOAD (kn) 120 100 80 Tyre Type VI TRAFFIC SPEED (3.39-4.38 m/s) ICAP 97 60 40 20 r 2 = 0.979 Std. Error of Y. = 4.3 kn 0 0 20 40 60 80 100 120 HVS APPLIED LOAD (kn) FIGURE 5 Accuracy of the VRSPTA relative to HVS applied load (random error)
ICAP 97
VERTICAL CONTACT STRESS, q (kpa) 11.00 x 20 14 ply smooth HVS Tyre ICAP 97 1000 900 800 700 600 500 400 300 830 630 520 620 AVERAGE (1974) 400 500 600 700 800 900 TYRE INFLATION PRESSURE, p (kpa) FIGURE 10 Average vertical contact stress vs inflation pressure MAXIMUM 95 P 90 P 80 P 50 P
ICAP 97
ICAP 97 VRSPTA Mark III
CONTACT STRESS (kpa) 1600 1400 Tyre Load = 18 kn INFLATION PRESSURE:: 420 kpa 520 kpa 620 kpa 720 kpa ICAP 97 1200 Tyre width: 220 mm 1000 800 600 400 200 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 PIN NUMBER ACROSS VRSPTA FIGURE 11 Maximum vertical stress at CONSTANT LOAD and various inflation pressures
CONTACT STRESS (kpa) 1600 1400 1200 1000 800 600 400 200 Tyre Load = 49 kn Tyre width: 220 mm INFLATION PRESSURE: 420 kpa 520 kpa 620 kpa 720 kpa ICAP 97 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 PIN NUMBER ACROSS VRSPTA FIGURE 12 Maximum vertical stress at CONSTANT LOAD and various inflation pressures
CONTACT STRESS (kpa) 1600 INFLATION PRESSURE = 420 kpa ICAP 97 1400 1200 WHEEL LOAD: 20kN 30kN 40kN 50kN 1000 800 600 400 200 Tyre width: 220 mm 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 PIN NUMBER ACROSS VRSPTA FIGURE 13 Maximum vertical stress at CONSTANT INFLATION PRESSURE at various loads
CONTACT STRESS (kpa) 1600 1400 1200 1000 800 600 400 200 INFLATION PRESSURE = 620 kpa WHEEL LOAD: 20kN 30kN 40kN 50kN Tyre width: 220 mm ICAP 97 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 PIN NUMBER ACROSS VRSPTA FIGURE 14 Maximum vertical stress at CONSTANT INFLATION PRESSURE and various loads
CONTACT STRESS (kpa) Tyre Load = 20 kn ICAP 97 1600 1400 1200 1000 800 600 400 200 0 TYRE INFLATION PRESSURE: 420 kpa 520 kpa 620 kpa 720 kpa 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 PIN NUMBER OF VRSPTA FIGURE 16 Maximum vertical stress of tyre with tread grooves at CONSTANT LOAD and various inflation pressures
CONTACT STRESS (kpa) ICAP 97 1600 1400 1200 1000 800 600 400 200 INFLATION PRESSURE = 520 kpa TYRE LOAD (kn): 42 30 26 20 15 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 PIN NUMBER OF VRSPTA FIGURE 17 Vertical stress of tyre with tread grooves at CONSTANT INFLATION PRESSURE and various loads
% CUM FREQUENCY 10.00 X 20 14 PLY TYRE WITH TREAD ICAP 97 100 90 80 70 60 50 40 30 20 10 TYRE LOAD: 14 kn 17 kn 31 kn 40 kn 0 0 200 400 600 800 1000 1200 1400 1600 1800 2000 22 kn INTERVAL MIDPOINT CONTACT STRESS (kpa) FIGURE 19 Cumulative frequency of maximum vertical stress
ICAP 97 DIRECTION OF TRAVEL 94 296 452 560 644 705 750 781 804 816 817 808 793 764 724 674 606 519 407 252 73 213 508 677 771 827 860 881 894 902 906 906 910 909 905 905 899 889 878 860 832 794 727 616 438 171 96 440 606 677 699 711 713 713 722 722 718 724 724 724 727 729 732 730 728 724 726 724 714 686 613 424 125 190 565 728 795 812 825 825 825 831 832 828 837 835 833 832 837 839 837 833 827 824 822 813 794 742 574 235 182 437 591 665 695 712 721 727 729 732 733 733 734 732 734 733 732 728 726 717 708 681 616 465 219 94 327 478 570 674 695 724 773 754 773 795 765 783 772 723 726 670 582 514 362 148 110 216 291 352 397 415 421 415 376 339 283 206 129 50 MEASURED VERTICAL CONTRACT STRESS VALUES FIGURE 25d Patch area = 74 028 mm 2 Typical measured tyre contact patch
VERTICAL CONTACT STRESS (kpa) 1200 TYRE TYPE I (HVS SMOOTH) (11.00 X 20, 14 Ply) ICAP 97 1000 800 600 Inflation Pressure: 400 kpa 600 kpa 800 kpa 400 10 20 30 40 50 SINGLE TYRE LOAD (kn) FIGURE 26a Maximum vertical stress vs tyre load
VERTICAL CONTACT STRESS (kpa) TYRE TYPE II (HVS - WITH TREAD) (11.00 X 20, 14 Ply) 1600 1500 ICAP 97 1400 1300 1200 1100 1000 900 Inflation Pressure: 800 kpa 600 kpa 400 kpa 5 10 15 20 25 30 35 40 45 SINGLE TYRE LOAD (kn) FIGURE 26b Maximum vertical stress vs tyre load
VERTICAL CONTACT STRESS (kpa) 2280 2260 2240 2220 2200 2180 2160 2140 2120 TYRE TYPE III (AIRCRAFT TYRE) Inflation Pressure: 1448 kpa ICAP 97 2100 15 20 25 30 35 40 45 50 55 SINGLE TYRE LOAD (kn) FIGURE 26c Maximum vertical stress vs tyre load
VERTICAL CONTACT STRESS (kpa) 3000 2500 2000 TYRE TYPE IV (315/80 R22.5) Inflation Pressure: ICAP 97 1200 kpa 1000 kpa 800 kpa 600 kpa 400 kpa 1500 1000 500 20 40 60 80 100 120 SINGLE TYRE LOAD (kn) FIGURE 26d Maximum vertical stress vs tyre load
VERTICAL CONTACT STRESS (kpa) 2400 2200 2000 1800 TYRE TYPE V (425/65 R22.5 - WIDE BASE) Inflation Pressure: 1200 kpa 1000 kpa 800 kpa 600 kpa 400 kpa ICAP 97 1600 1400 1200 1000 20 40 60 80 100 120 SINGLE TYRE LOAD (kn) FIGURE 27a Maximum vertical stress vs tyre load
VERTICAL CONTACT STRESS (kpa) 2400 2200 2000 1800 TYRE TYPE VI (425/65 R22.5 - R160AZ WIDE BASE) ICAP 97 Inflation Pressure: 1200 kpa 1000 kpa 800 kpa 600 kpa 400 kpa 1600 1400 1200 1000 800 20 40 60 80 100 120 SINGLE TYRE LOAD (kn) FIGURE 27b Maximum vertical stress vs tyre load
VERTICAL CONTACT STRESS (kpa) 2200 2000 1800 TYRE TYPE VII (425/65 R22.5 - R160BZ - WIDE BASE) Inflation Pressure: 1200 kpa 1000 kpa ICAP 97 1600 1400 1200 800 kpa 600 kpa 400 kpa 1000 800 20 40 60 80 100 120 SINGLE TYRE LOAD (kn) FIGURE 27c Maximum vertical stress vs tyre load
ICAP 97 DEPTH (mm) 0 50 200 360 470 610 ASPHALT STABILIZED LAYERS SELECTED LAYER RIVER SAND LAYER IN SITU FERRICRETE FIGURE: 28 Pavement structures evaluated with the HVS
Radial Distance (mm) ICAP 97 1 300 600 100 0 Non-Uniform Vertical Stress Depth (mm) 0 40 Tyre Edge Lateral stress CL 200 1 300 FIGURE: 29 Axi-symmetrical Finite Element Model used in this study
TYPE I CL 520 kpa (Vertical) ICAP 97 II 520 kpa (Vertical) III 520 kpa (Vertical) IV 520 kpa (Vertical) 260 kpa (Inward Shear) V 520 kpa (Vertical) 260 kpa (Outward Shear) FIGURE: 30 Load/Contact Stress Idealizations used for the analysis in this study
LC ICAP 97 Rib 3 Rib 1 Rib 2 Rib 4 Rib 5 TYPE VI - TYRE CENTRE (Vertical and lateral) Rib 1 Rib 2 Rib 3 Rib 4 Rib 5 TYPE VII - TYRE EDGE (Vertical and lateral
ICAP 97
ICAP 97
ICAP 97 Pseudo-Energy under non-uniform contact stress conditions (Symplectic Engineering Corporation, USA)
ICAP 97 Colour maps of Shape distortion (Symplectic Engineering Corporation)
ICAP 97
ICAP 97 VRSPTA Mark III
Light Passenger Vehicle: Vertical Contact Stress
Light Passenger Vehicle: Lateral Contact Stress
Light Passenger Vehicle: Longitudinal Contact Stress
ICAP 97
ICAP 97
ICAP 97
Deflectograph Truck (80kN,650 kpa): Vertical Contact Stress
Deflectograph Truck (80kN,650 kpa): Lateral Contact Stress
Deflectograph Truck (80kN,650 kpa): Longitudinal Contact Stress
% Cumulative Frequency 100 DEFLECTOGRAPH (OCTOBER 1998) Test 038-z ICAP 97 80 60 40 20 690 kpa (Rear) 600 kpa (Front) 520 kpa (Design) 0 0 200 400 600 800 1000 1200 Measured Tire Contact Stress (kpa) Tyre Front Left Front Right Rear Left OuterRear Left InnerRear Right OuterRear Right Inner Inflation Pressure 600 kpa 600 kpa 690 kpa 690 kpa 690 kpa 690 kpa
ICAP 97 N1 Mantsole Weighbridege
ICAP 97
Maximum axle load legally allowed on South African Roads from 1996 Type of axle Single axle (steering) Single axle (nonsteering) No of tyres per axle Axle Mass (kg) 2 or 3 7 700 (7 700) 76 2 or 3 8 000 (7 700) 78 Single axle 4 or more 9 000 (8 200) 88 Tandem axle 4 or more 18 000 (16 400) 88 ICAP 97 Load per Axle (kn)* Tridem axle 4 or more 24 000 (21 000) 78,3 ( ) Previous legal load limits * g = 9,8 m/s 2
100 kn Axle WHEEL LOAD 25 kn 25 kn 25 kn 25 kn Road Category [TRH4 (1996)] Percentile Values (%) Contact Stress (kpa) Load Radius (mm) D 50 660 110 C 80 865 96 B 90 975 90 A 95 985 90 RECOMMENDED (INTERIM) TYRE CONTACT STRESSES
% Cumulative Frequency 100 DEFLECTOGRAPH (OCTOBER 1998) Test 038-z ICAP 97 80 60 40 20 690 kpa (Rear) 600 kpa (Front) 520 kpa (Design) 0 0 200 400 600 800 1000 1200 Measured Tire Contact Stress (kpa) Tyre Front Left Front Right Rear Left OuterRear Left InnerRear Right OuterRear Right Inner Inflation Pressure 600 kpa 600 kpa 690 kpa 690 kpa 690 kpa 690 kpa