Crashworthiness of High Speed Rail Systems
Total Page:16
File Type:pdf, Size:1020Kb
CRASHWORTHINESS OF HIGH-SPEED RAIL SYSTEMS A thesis Submitted by Laura Sullivan In partial fulfillment of the requirements For the degree of Master of Science In Mechanical Engineering TUFTS UNIVERSITY November 2011 Adviser: Professor Douglas Matson i Abstract Rail crashworthiness research focuses on the ability of passenger rail equipment to protect its occupants in the event of a collision. The goal of this research is to explore current high-speed trainsets and determine the level of structural crashworthiness they can provide to the occupant. One of the most effective ways of providing structural crashworthiness is through crash energy management. A crash energy management system (CEM) utilizes energy absorbing crushable elements and a strong vehicle structure to disperse collision energy in a controlled manner and provide protection to passengers. A survey of high-speed rail systems currently in operation was performed to determine appropriate equipment characteristics. An appropriate collision scenario was selected by reviewing accidents involving high speed equipment. Occupant safety was assessed by examining the performance of the equipment in the chosen collision scenario by using a one-dimensional lumped-parameter collision dynamics model to simulate a series of collisions. The features of interest are the energy absorbing capacity of the crush zone and the strength of the occupied volume and the influence that each of these features has on structural crashworthiness. Key results examined include the maximum collision speed without loss of occupant space, the distribution of crush throughout the cars of the train, and the severity of the deceleration experienced by the passengers. ii Table of Contents List of Appendices .....................................................................................iv List of Tables .............................................................................................iv List of Figures............................................................................................iv 1. Introduction......................................................................................... 1 2. Background ........................................................................................ 5 2.1. How is Structural Crashworthiness Achieved.............................. 7 2.1.1. Previous Research .................................................................. 9 2.1.2. Existing Technology............................................................... 17 2.2. Analysis Techniques ................................................................. 21 2.3. Analysis Goals .......................................................................... 22 3. Approach.......................................................................................... 24 3.1. Force-Displacement Characteristics.......................................... 28 3.1.1. Baseline Force-Displacement Characteristics.................... 30 3.1.2. Energy Adjustment............................................................. 36 3.1.2.1. Stroke Length Strategy................................................... 36 3.1.2.2. Force Level Strategy ...................................................... 39 3.1.3. Crippling Load Adjustment ................................................. 42 3.2. Safety Performance Assessment .............................................. 45 4. Results and Discussion .................................................................... 47 4.1. Safe Speed ............................................................................... 48 4.1.1. Energy Capacity Adjustment - Stroke Length Strategy ...... 50 4.1.2. Energy Capacity Adjustment - Force Level Strategy.......... 51 4.1.3. Crippling Load Adjustments – Cars of Equal Strength ....... 52 4.1.4. Crippling Load Adjustments – Stronger Leading Car ......... 56 4.1.5. Safe Speed Summary ........................................................ 57 4.2. SIV ............................................................................................ 58 4.2.1. SIV Results – Stroke Length Strategy................................ 60 4.2.2. SIV Results – Force Level Strategy ................................... 61 4.2.3. SIV Summary..................................................................... 62 4.3. CEM Utilization.......................................................................... 63 4.3.1. Energy Utilization – Stroke Length Strategy....................... 65 4.3.2. Energy Utilization– Force Level Strategy ........................... 66 4.3.3. Utilization Summary ........................................................... 67 iii 5. Summary.......................................................................................... 68 6. Conclusions...................................................................................... 71 List of Appendices Appendix 1: Force-Displacement Characteristics of Vehicle Structures .. 74 Appendix 2: CEM Equipment Survey ...................................................... 87 Appendix 3: Force – Displacement Approximations .............................. 101 Appendix 4: Accident Survey................................................................. 107 List of Tables Table 1: Crush Zone Energy Capacities - Stroke Length Adjustments.... 38 Table 2: Crush Zone Energy Capacities - Force Level Adjustments ....... 41 Table 3: Crippling Load Combinations Analyzed..................................... 44 Table 4: Allowable Crush at Each End .................................................... 50 Table 5: Safe Speed Results................................................................... 56 Table 6: Summary of High Speed Equipment Composition..................... 99 Table 7: Summary of High Speed Equipment CEM information............ 100 Table 8: Summary of Accident Survey .................................................. 122 List of Figures Figure 1: TGV Duplex Schematic ............................................................ 19 Figure 2: Acela Schematic....................................................................... 20 Figure 3: Collision Schematic .................................................................. 25 Figure 4: Trainset Schematic with Locations labeled............................... 27 Figure 5: Crush Zone Schematic............................................................. 28 Figure 6: Generic Force-Displacement Characteristic ............................. 29 Figure 7: Draft Gear Force-Displacement................................................ 30 Figure 8: Collision-end Pushback Coupler Force-Displacement.............. 31 Figure 9: Baseline Collision-end PEA Force-Displacement..................... 33 Figure 10: Baseline Occupant Volume Force-Displacement ................... 34 Figure 11: Baseline CEM System Force-Displacement........................... 35 Figure 12: Stroke Length Adjustments .................................................... 37 Figure 13: Force Level Adjustments ........................................................ 39 Figure 14: Crippling Load Adjustments.................................................... 42 Figure 15: Allowable Crush v. Occupant Volume Intrusion...................... 45 Figure 16: Crush Results for the Baseline Case at 26 mph..................... 49 Figure 17: Stroke Length Adjustment Strategy........................................ 51 Figure 18: Force Level Adjustment Strategy ........................................... 52 Figure 19: Crippling Load Adjustments to Baseline Energy Capacity...... 53 Figure 20: Variations in Crippling Load and Stroke Length ..................... 54 iv Figure 21: Variations in Crippling Load and Energy Absorber Force Level ................................................................................................................ 55 Figure 22: Relative Acceleration of Passengers within the Trainset........ 60 Figure 23: SIV Results at 3 ft – Stroke Length Adjustments................... 61 Figure 24: SIV Results at 3 ft –Force Level Adjustments ........................ 62 Figure 25: Baseline System Energy Utilized at Safe Speed .................... 64 Figure 26: CEM Utilization – Stroke Length Adjustment Strategy............ 65 Figure 27: CEM Utilization – Force Level Adjustment Strategy ............... 66 Figure 28: Safe Speed Results – Strategy Comparison .......................... 67 Figure 29: Example Force Displacement Collision Dynamics Input......... 74 Figure 30: Example Acceleration for Vehicle CG in a collision ................ 75 Figure 31: Force Applied to a Spring-Mass system ................................. 76 Figure 32: Force Applied to an Expanded Spring-Mass System ............. 77 Figure 33: Relative Force Displacement Behavior................................... 78 Figure 34: Increasing Stages of the Crush Zone ..................................... 79 Figure 35: Activation Force...................................................................... 80 Figure 36: Sloped Force Level................................................................. 81 Figure 37: Drop out in Force.................................................................... 82 Figure 38: Energy Absorbed by the Crush Zone ..................................... 83 Figure 39: Draft Gear and Coupler Schematics....................................... 84 Figure 40: Components of the Crush Zone ............................................. 85 Figure 41: The Crush Zone and Occupied Volume ................................