MILITARY trainees, especially those who are volunteers and those who plan to be officers, must expect to undergo mental and physical challenges they might not face in civilian life. But another kind of challenge - hazing - continues to occur, even though it is officially forbidden at the three United States service academies.Much of the hazing has, in recent years, been directed at women cadets in the three US military academies or other institutions that turn out officers. A September 1990 report issued by the Pentagon said that 64 percent of military women surveyed indicated they had been sexually harassed, either physically or in subtler ways. It is time to lay to rest the myth that such activities contribute to character-building. For many years hazing in some form was tacitly condoned in both military and civilian settings. With regards to women students at military academies, the problem has reached a critical point in the last two or three years. In December 1990, several male cadets at the US Naval Academy in Annapolis, Md., handcuffed a female plebe to a urinal in the barracks. The woman cadet - daughter and granddaughter of Naval Academy graduates - resigned after the experience. Two of her tormenters were given demerits and lost furlough time; six others received written admonishments. Commanders who fail to quickly respond to instances of sexual harassment have been given warning: In November a Navy rear admiral was removed from his command at Patuxent River Naval Air Test Center in Maryland for "apparent failure to take timely and appropriate action" on a woman lieutenant's charge that she and five other servicewomen were verbally and physically abused by drunken junior aviators. Surely familiarity, mutual respect, and logic must displace male chauvinism at the service academies and in other military settings. There is no legitimate role for physical and psychological abuse of women in the training of military leaders.