QUENCH AND PARTITION STEELS FIND WIDE USE IN THE AUTOMOTIVE INDUSTRY BECAUSE OF THEIR HIGH CAPABILITY OF ENERGY ABSORPTION. INDUSTRIAL DEMANDS HAVE PROMPTED THE EXPANSION OF THIS RESEARCH FIELD BECAUSE OF THE INFLUENCE THESE MATERIALS HAVE ON COMPONENTS THAT CAN ABSORB HIGH ENERGY OF IMPACT TO REDUCE PASSENGER DAMAGE, FOR EXAMPLE. THE PARTITION PROCESS'S DIFFICULTIES LIE MAINLY IN CONTROLLING THE THERMODYNAMICS AND THE KINETICS OF THE PHASE TRANSFORMATION. BOTH AFFECT ACHIEVING ADEQUATE AUSTENITE RETENTION AND OPTIMAL MECHANICAL PROPERTIES. MANY RESEARCHERS HAVE ATTEMPTED TO INCREASE THESE MATERIALS' ENERGY ABSORPTION EFFICIENCY BY INCORPORATING MICROALLOYING ELEMENTS THAT CONTROL PHASE TRANSFORMATION DURING THE PARTITIONING PROCESS, TYPICALLY DONE IN THREE STEPS. HOWEVER, NO RESEARCH HAS BEEN CARRIED OUT ON THIS TOPIC USING NB AND SI MICROALLOYING ON LOW-CARBON STEELS IN TWO STAGES. THEREFORE, AN ALLOY WAS DESIGNED AND MODELLED WITH MECHANICAL REINFORCEMENT BY PRECIPITATION AND TRANSFORMATION-INDUCED PLASTICITY (TRIP), DOPING THE STEEL WITH NB AND SI IN A TWO-STAGE QUENCHING AND PARTITIONING PROCESS. THEN, STEEL SAMPLES WERE FABRICATED TO VALIDATE THE MODEL. THERE WERE TWO GROUPS OF SAMPLES WITH DIFFERENT DIMENSIONS TO EVALUATE THE SENSITIVITY OF AUSTENITE RETENTION CONCERNING THE SAMPLE THICKNESS. THE MAIN RESULTS SHOWED THAT 10.75% OF RETAINED AUSTENITE ALLOWS AN ENERGY ABSORPTION OF 30.55 GPA% WITH A TWO-STAGE QUENCHING AND PARTITIONING HEAT TREATMENT. SAMPLE THICKNESS INFLUENCES AUSTENITE RETENTION DUE TO DIFFUSION KINETICS DURING THE PARTITIONING PROCESS. FINALLY, VIRTUAL TESTS QUANTIFIED THE UNIT STRAIN ENERGY ABSORPTION OF THE RETAINED AUSTENITE AT 1.9 MJ AT 25 °C.

DYNAMIC JOINT-FORCES IN A MECHANISM PRODUCE VIBRATION AND WEAR, DECREASING ITS LIFE SPAN. MANY STUDIES HAVE BEEN CARRIED OUT ON OPTIMIZATION OF MECHANISMS DYNAMIC BEHAVIOUR; HOWEVER, FEW OF IT ARE FOCUSED ON THE REDUCTION OF JOINT-FORCES. THEREFORE, THIS WORK PRESENTS A METHOD TO OBTAIN THE LINK LENGTHS OF FUNCTION GENERATION FOUR-BAR LINKAGES, MINIMIZING THE MAXIMUM DYNAMIC FORCE IN THE JOINTS. THE STUDY ASSUMES THAT THE CRANK ROTATES WITH CONSTANT ANGULAR VELOCITY AND THE ROCKER MOVES A HIGH AMOUNT OF INERTIA BETWEEN TWO POSITIONS. HENCE, THE MECHANISM MASS AND INERTIA IS CONSIDERED NEGLIGIBLE. THE EQUATIONS OF MOTION ARE SET UP TOGETHER WITH DEAD-CENTER CONSTRUCTION METHOD AFTER ALT. TO ANALYZE THE BEHAVIOUR OF THE JOINT-FORCES, ALL THE EQUATIONS ARE PARAMETRIZED, FINDING OUT THAT THE MAXIMUM JOINT-FORCE IS MINIMIZABLE FOR EVERY TASK GIVEN. THE MINIMIZATION OF THE JOINT-FORCES IS ACHIEVED BY USING SIMPLE ALGORITHMS AS BISECTION AND REGULA-FALSI ILLINOIS. THE RESULTS SHOW THAT THIS METHOD REDUCES THE MAXIMAL JOINT-FORCE BY A MEAN VALUE OF 8.5%, WITH RESPECT TO THE DEAD-CENTER CONSTRUCTION METHOD WITH TRANSMISSION ANGLE MINIMIZATION. MOREOVER, FOR SOME TASKS, THE FORCE REDUCTION COULD REACH UP TO 60%. FURTHERMORE, THIS METHOD SOLVES THE PROBLEM OF NULL-LENGTH CRANK AND ROCKER FOR CENTRIC CRANK-ROCKER MECHANISMS, GENERATED BY THE TRANSMISSION ANGLE MINIMIZATION.

WAVE ENERGY HAS ENORMOUS POTENTIAL AND MANY GOOD QUALITIES, SUCH AS ITS PREDICTABILITY, ENERGY DENSITY AND LOW VARIABILITY. NEVERTHELESS, THIS TYPE OF ENERGY STILL NEEDS TO BE COMPETITIVE AGAINST OTHER TYPES OF RENEWABLE ENERGY, LIKE WIND OR SOLAR ONES. THIS IS MAINLY DUE TO ITS HIGH COST. ONE SOLUTION TO REDUCE THE COST OF WAVE ENERGY IS THE USE OF CONTROL STRATEGIES. IN THIS WORK, A SIMPLE POINT ABSORBER BASED ON THE DIMENSIONS OF AN ONGOING PROJECT, NAMED LAFKENEWEN, IS MODELED WITH LINEAR POTENTIAL THEORY AND THE SOFTWARE ANSYS-AQWA. THREE DIFFERENT CONTROL STRATEGIES, REACTIVE CONTROL, LATCHING CONTROL AND RESISTIVE CONTROL, ARE COMPARED FOR A REGULAR WAVE THAT REPRESENTS THE MEAN SEA STATE OF THE PROJECT SITE LOCATION. RESULTS SHOW THAT THE REACTIVE CONTROL CAN ACHIEVE UP TO 18 KW BUT FOR UNREALISTIC CONDITIONS. LATCHING CONTROL ALLOWS CONVERTING UP TO 4 KW SHOWING BETTER PERFORMANCE THAN THE RESISTIVE CONTROL, WHICH ONLY ALLOWS UP TO 0.8 KW AVERAGE.

MUCH RESEARCH HAVE BEEN CARRIED OUT TO SYNTHESIZE LINKAGES, YET A FEW IS CONCENTRATED ON THE DYNAMIC BEHAVIOR OF SIX BAR LINKAGES IN THE EARLY STAGES OF THE DESIGN PROCESS. THEREFORE, WE PRESENT A TWO-STEP SYNTHESIS METHOD FOR FUNCTION GENERATOR SIX-BAR LINKAGES THAT INCLUDES CONSTRAINTS RELATED TO THE DYNAMIC BEHAVIOR OF THE MECHANISM. THE FIRST STAGE FOCUSES ON MATCHING EIGHT GIVEN PRECISION POSITIONS AND THE SECOND STAGE ON MINIMIZING THE REACTION FORCES. BOTH MINIMIZATION PROBLEMS ARE SOLVED WITH A GENETIC ALGORITHM IN MATLAB?. THE RESULTS ARE COMPARED WITH A MULTI-BODY SIMULATION IN MSC ADAMS.

IN THE DESIGN PROCESS OF A MECHANISM, THE DYNAMIC BEHAVIOR PLAYS AN IMPORTANT ROLE. IT COULD BE THE CAUSE OF UNEXPECTED HIGH DYNAMIC FORCES IN LATER STAGES WHEN IT IS NOT CONSIDERED IN THE EARLY STAGE OF THE DESIGN PROCESS. HIGH FORCES COULD PRODUCE HIGH STRESSES AND HIGH VIBRATION LEVELS. SEVERAL STUDIES HAVE BEEN CARRIED OUT IN THIS AREA; HOWEVER, ONLY A FEW CONSIDER STRUCTURAL CRITERIA AND THE EIGENFREQUENCIES IN THE EARLY STAGE OF THE PROCESS. LOW FORCES AND AN ADEQUATE STRUCTURE SHOULD LEAD TO GOOD DYNAMIC BEHAVIOR. IN THIS WORK, WE PRESENT A METHOD TO SYNTHESIZE FUNCTION GENERATOR FOUR-BAR LINKAGES THAT TAKES INTO ACCOUNT STRUCTURAL CRITERIA IN A JOINT-FORCES MINIMIZATION-MAXIMIZATION PROBLEM. ITS OBJECTIVE FUNCTION IS THE REACTION FORCE ON THE MECHANISM JOINTS. THE PROBLEM?S CONSTRAINTS ARE THE MAXIMUM STRESS ON THE LINKS, THE FIRST EIGENFREQUENCY OF THE MECHANISM AND THE DEFLECTION OF THE CRANK AND THE ROCKER. WITH THIS METHOD, THE LINKS? LENGTHS AND CROSS-SECTIONAL AREAS OF THE MECHANISM ARE OBTAINED FOR A GIVEN TASK. AS CONDITION, WE ASSUMED THAT THE CRANK ROTATES WITH CONSTANT ANGULAR SPEED AND ITS SHAFT WORKS AS A TORSIONAL SPRING. MOREOVER, THE ROCKER MOVES A BODY WITH CONSTANT INERTIA. THE RESULTANT MECHANISMS ARE COMPARED WITH THOSE OBTAINED WITH A TRADITIONAL CRANK-ROCKER SYNTHESIS METHOD, ACCORDING TO VDI 2130. TO COMPARE BOTH METHODS, THE MAXIMUM FORCE, MAXIMUM STRESS, DEVIATION OF THE ROCKER ANGLE AT ITS DEAD-CENTER POSITIONS AND RMS VIBRATION OF THE CRANK AND ROCKER OF EACH MECHANISM ARE CALCULATED USING MSC ADAMS?. THE RESULTS SHOW THAT THE MECHANISMS OBTAINED WITH OUR METHOD HAVE BETTER STRESS AND VIBRATORY LEVELS THAN THOSE OBTAINED WITH A TRADITIONAL APPROACH.