On November 21, 2007, about 1615 Pacific standard time, a Beech 95-B55 airplane, N1831L, was substantially damaged when the nose wheel landing gear collapsed during landing roll at the Mc Clellan-Palomar Airport (CRQ), Carlsbad, California. The airline transport pilot and his passenger were not injured. The airplane was registered to a private individual and operated by the pilot. Visual meteorological conditions prevailed and a flight plan was not filed for the 14 Code of Federal Regulations Part 91 personal flight. The local flight originated from CRQ at 1559. According to the pilot, as the nose wheel landing gear settled onto the runway during landing, he felt a strong vibration in the rudder pedals. The pilot "abruptly" applied backpressure on the control yoke and the airplane became airborne. As he relieved the backpressure on the control yoke, the airplane landed on the nose wheel landing gear and "started to porpoise." The pilot stated that after the fourth oscillation, he applied full backpressure, and as the airplane slowed, he initiated a turn onto a taxiway. As the airplane exited the runway, the nose of the airplane settled onto the asphalt surface. Examination of the airplane by a Federal Aviation Administration (FAA) inspector revealed that the fuselage was buckled along the cabin area above the left and right wing roots. The nose wheel was found separated from the piston and fork assembly. No anomalies were noted with the flight control system or nose wheel fork and strut assembly. The separated portion of the nose wheel assembly was sent to the NTSB Office of Research and Engineering, Materials Laboratory Division for further examination. Examination of the nose wheel rim revealed that the inboard half of the wheel rim was fractured and the outboard half of the wheel rim was deformed and cracked. The Senior Materials Engineer reported that the fracture features and deformation of both halves were consistent with overstress fractures. No evidence of preexisting cracks was observed. The nose wheel axel was separated into two portions, with the outboard piece remaining in the nose wheel and inboard piece remaining in the nose wheel strut. The fracture surface of the axel was on slant planes and exhibited matte gray features consistent with overstress fractures. No evidence of preexisting cracks was observed. The portion of the axel remaining in the nose wheel was removed. The inner race and rolling elements of the left bearing were displaced about 0.6 inches to the left. The axle was bent in the area of the displaced left bearing location. The upper surface of the axle exhibited a circumferential crack at the location corresponding to the right edge of the left bearing inner race. An impact mark was observed on the upper surface of the axle consistent with heavy contact to the left bearing inner race in its assembled location.